Heat exchanger



Oct. 14, 1941. w. H. KITTO HEAT EXCHANGER Filed Nov. 15, 1937 INVENTORZlzam H Kiflo ATTORNEY Patented Oct. 14, 1941 HEAT EXCHANGER I WilliamH. Kitto, Canton, Ohio, assignor to The Hoover Company, North Canton,Ohio, a corporation of Ohio Application November 15, 1937, Serial No.174,601

. 4 Claims. (01. 29-1573) This invention relates to the art of makingtubular structures and more particularly to fluid heat exchangersfabricated from standard tubmg.

It is commonplace to utilize tubing of different diameters to mak heatexchangers by inserting a smaller tube in a large tube, and then bendingthe telescoped tubes into a desired shape. Such constructions are easilymade from standard, readily obtained materials. This form of heatexchanger is very eflicient, inexpensive and free from sharp bends.

However, prior art heat exchangers of this type are subject to certaindisadvantages. One of the chief difficulties is that in making theconcentric tube heat exchanger, the operator has no control' over theinner tube. Consequently, in bending thetubes into a desired shape, thebending operations are directly applied to the outer tube, and onlyindirectly to the inner tube. As a result, the inner tube is notcoaxially positioned within the outer tube, and the inner tube may lieclosely against the inside wall of the outer tube adjacent the bends.Therefore, the fluid passing between two tubes is greatly impeded wherthe tubes lie close together, and the'heat exchange is poorest where theinner wall of the outer tube is furtherest from the inner tube.

According to this invention, I propose simple modifications in theconstructions heretofore known which permit the retention of the manydesirable characteristics of concentric tube heat exchangers and yetentirely avoid the disadvantages herelnabove pointed out, as well asothers of lesser importance.

It is accordingly an object of my invention to provide a new andimproved heat exchanger. More specifically it is an object of fnyinvention to provide a heat exchanger having inner and outer tubes andmeans for spacing the tubes with respect to each other. Another objectis to provide means for spacing the curved sections of telescoped tubeswith respect to each other. A further object is to provide means forconnecting a transverse tube to curved telescoped tubes. Another objectis to provide methods of making heat exchangers. Other objects andadvantages of the invention will be apparent in the specification anddrawing, wherein:

Fig. #1 is a perspective view of the heat exchanger;

Fig. 2 is a section along the line 2-2 of Fig. 1;

Fig. 3 is a section along the line 3-3 of Fig. 1;

Fig. 4 is a section similar to Fig. 3 illustratin: another embodiment ofthe invention.

The heat exchanger shown in Figures 1 through 3 comprises telescopedmetal tubes i0 and II coiled as indicated in Fig. 1 to provide arcuatebends l2 and i3 and straight portions 14. The outer tube Ii has its ends15 sealed to the projecting ends of the inner tube I0. Welded to theouter tube II along the inner arc of the bend i3 is a transverse pipei1, and a pipe I8 is welded to the opposite end of th outer tube II, andwhich communicate with an annual passageway is formed between thetelescoped tubes 10 and Ii to provide passage for the fluidtherethrough.

The arcuate bends i2 and 13 are formed by bending the telescoped tubesas a unit. In the bending operation the operator has control of theouter tube ii and can bend it into any desired degree of curvature. Theinner tube in, however, is not under the control of the operator but isbent by th pressure exerted thereon by the outer tube I. In forming, forexample the bend I3 as shown in Figure 3, the inner tube in tends totake a flatter arc than the outer tube ii, so that the center portion 20in the bend of the inner tube [0 tends to bear against the center of theinner arc of the outer tube II, and the opposite ends 22 on the outerarc of the inner tube [0 tend to bear against the opposite ends 23 onthe outer arc of the outer tube ii, to thereby interrupt flow of fluidin the passageway 19 and to the transverse tube [1.

One method of correcting this objectionable construction is shown inFigures 1 to 3, wherein the outer tube II is provided withlongitudinally circumferentially spaced indentations 25 throughout thecurved or arcuate portions thereof. These indentations bear against theinner tube ill to space it in concentric relation with respect to theouter tube l I throughout the curved portions l2 and I3. If inner tubeI0 is co-axially positioned in outer tube H at the curved portions ofthe exchanger, the straight sections of tubes I0 and H will be retainedin co-axial relation in the unbent portions H of the heat exchanger. Thetransverse tube H is welded, as indicated at 26 in the opening 24 to theouter tube I I, and due to the indentations 25 communicates freely withthe annual passage l9.

One method of making a heat exchanger of this type consists of formingthe openings 24 at desired point or points in the outer tube II for thedesired number of transverse tubes l1 and I8, inserting the smaller tubeIII in the outer tube ll, forming groups of spaced-apart dimplesorindentations 25 longitudinally and circumferentially around the outertube ll wherever the same is to be bentor curved, bending both tubes asa. unit into a coil so that a group of indentations is located at eachbend as shown in Fig. 1, and then welding the transverse pipes l1 and I8to the outer pipe II. If desired the dimpies may be formed in the outertube prior to inserting the smaller tube, and the transverse pipes may bwelded to the outer pipe prior to "bending the tubes into a coil.

outer tube II, to space the inner tube from the.

opening 36 to provide an uninterrupted path for fluid between thetransverse pipe llv and the annular passage 19. If desired, indentationsmay be provided at substantially the opposite ends of the outer are onthe outer tube II to space the inner tube Hi from the outer tube llthroughout the length of the bend.

Ifit is desired to form a heat exchanger employing this construction theouter tube II is provided at a certain point or points with the desirednumber of openings 36 and the smaller tube I is arranged within thelarger tube I l and the indentations 35 are formed in the outer tube IIin the vicinity of the openings 36. The two tubes are then bent as aunit into the desired shape. Due to the indentations 35 the inner tubeIII will be spaced from the inner arc of the outer tube II at theopening 36.

Although the indentations have, been described as located at the bent orcurved portions of the tubes, it will be understood that theindentations may be distributed over straight sections of tubing as wellto assure co-axial positioning of the tubes throughout the length of theheat exchanger. Where the straight sections of tubing are short, as inFigure 1, it is not usually necessary to locate indentations in thestraight portions.

It will thus be apparent that the present invention provides a new andsimple method of constructing a concentric tube type heat exchangerespecially suited for mass production. A minimum number of dies, tools,implements,

and operations are required. The only change 'a heat exchangerconstruction which is very simple, economical, and highly eflicient inoperation, as well as one in which the heat exchange fluids flow freelyto and from the exchanger, as well as through the respective passages01' the exchanger.

I claim:

l. A heat exchanger, comprising an outer tube, an inner tube disposed inand spaced from said outer tube, said tubes being bent to form a coiledheat exchanger, a tube connected to and extending laterally from saidouter tube along the inner arc of one of said bends, and indentations inthe wall of one of said tubes along said inner arc of said tube bend forspacing said inner tube from said outer tube to provide a passagewaybetween said spaced pipes and said transverse tube to facilitate thefree passage of a fluid between said laterally extending tube and saidheat exchange coil.

2. That .method of constructing a fluid heat exchanger which comprisescutting lengths of tubing of different diameters into sections ofpredetermined length, the sections of smaller diameter tubing beinglonger than the sections of larger diameter tubing, inserting a sectionof smaller diameter tubing into a section of larger diameter tubinguntil the ends of the smaller tubing project beyond both ends of thelarger tubing, placing groups of indentations in the surface of' thelarger tubing at spaced points therealong which indentations are ofsufllcient size and spaced in such manner as to retain said smaller andlarger sections in a definite position with respect to one another, andthen bending said tubing sections at said groups of indentations to forma coil having a substantially continuous annular fluid passage betweensaid tubing sections from the inlet to the outlet thereof.

3. A heat exchange device comprising two continuous conduit sections oneof which is of smaller diameter than the other, said smaller sectionbeing positioned within the larger section so as to provide'two fluidpassageways one of which is through the smaller section and the other ofwhich is between said smaller and larger conduits, said smaller conduitbeing longer than the larger conduit so as to extend beyond the ends ofthe latter, said conduit sections being bent into a coil, and groups ofindentations in said larger conduit positioned so as to prevent thesmaller conduit from contacting the inner surface of the larger conduitexcept at said indentations, said groups of indentations being locatedat the coil bends.

4. A heat exchange device as defined in the preceding claim in which thelarger conduit has an opening through the side thereof, a conduit joinedto the larger conduit over said opening,

and indentations in said larger conduit adjacent I said opening to holdthe inner, smaller conduit away from said opening to permit the freepassage of fluid through said opening.

WILLIAMH.KI'I'TO.

